Systems and methods for an improved peel operation during additive fabrication

ABSTRACT

According to some aspects, a method of additive fabrication wherein a plurality of layers of material are formed is provided. The method may comprise forming a layer of material in contact with a container, and subsequent to the forming of the layer of material, actively bending the container around at least one fixed point such that the layer of material separates from the container. According to some aspects, an additive fabrication apparatus configured to form a plurality of layers of material is provided. The apparatus may comprise a container, a build platform, one or more force generators, and at least one controller configured to, subsequent to formation of a layer of material in contact with the container, actively bend the container around at least one fixed point via the one or more force generators, such that the layer of material separates from the container.

FIELD OF INVENTION

The present invention relates generally to systems and methods forseparating a part from a surface during additive fabrication, e.g.,3-dimensional printing.

BACKGROUND

Additive fabrication, e.g., 3-dimensional (3D) printing, providestechniques for fabricating objects, typically by causing portions of abuilding material to solidify at specific locations. Additivefabrication techniques may include stereolithography, selective or fuseddeposition modeling, direct composite manufacturing, laminated objectmanufacturing, selective phase area deposition, multi-phase jetsolidification, ballistic particle manufacturing, particle deposition,laser sintering or combinations thereof. Many additive fabricationtechniques build parts by forming successive layers, which are typicallycross-sections of the desired object. Typically each layer is formedsuch that it adheres to either a previously formed layer or a substrateupon which the object is built.

In one approach to additive fabrication, known as stereolithography,solid objects are created by successively forming thin layers of acurable polymer resin, typically first onto a substrate and then one ontop of another. Exposure to actinic radiation cures a thin layer ofliquid resin, which causes it to harden and adhere to previously curedlayers or the bottom surface of the build platform.

SUMMARY

Systems and methods for separating a part from a surface during additivefabrication are provided.

Some embodiments include a method of additive fabrication wherein aplurality of layers of material are formed on a build platform,comprising forming a layer of material in contact with a container, andsubsequent to the forming of the layer of material, actively bending thecontainer around at least one fixed point such that the layer ofmaterial separates from the container.

Some embodiments provide an additive fabrication apparatus configured toform a plurality of layers of material on a build platform, comprising acontainer, the build platform, one or more force generators, and atleast one controller configured to subsequent to formation of a layer ofmaterial in contact with the container, actively bend the containeraround at least one fixed point via the one or more force generators,such that the layer of material separates from the container.

Some embodiments provide at least one computer readable mediumcomprising instructions that, when executed, perform a method ofadditive fabrication wherein a plurality of layers of material areformed on a build platform, the method comprising forming a layer ofmaterial in contact with a container, and subsequent to the forming ofthe layer of material, actively bending the container around at leastone fixed point such that the layer of material separates from thecontainer.

The foregoing summary is provided by way of illustration and is notintended to be limiting.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings are not intended to be drawn to scale. Forpurposes of clarity, not every component may be labeled in everydrawing. In the drawings:

FIG. 1 provides a schematic view of a stereolithographic printer,according to some embodiments;

FIG. 2 provides a schematic view of a stereolithographic printer havingformed a plurality of layers of a part, according to some embodiments;

FIG. 3 illustrates a mechanical operation for separating a part from asurface of a stereolithographic printer, according to some embodiments;

FIGS. 4A-B depict a first exemplary additive fabrication deviceconfigured to separate a part from a surface by bending the surface,according to some embodiments;

FIGS. 5A-B depict a second exemplary additive fabrication deviceconfigured to separate a part from a surface by bending the surface,according to some embodiments;

FIGS. 6A-C depict a stereolithographic printer utilizing a thin film,according to some embodiments;

FIGS. 7A-C depict wiping of a thin film in a stereolithographic printer,according to some embodiments;

FIG. 8 depicts application of pressure to a stereolithographic printerutilizing a thin film, according to some embodiments;

FIG. 9 illustrates a flow chart of a process suitable for separating apart from a surface during additive fabrication, according to someembodiments; and

FIG. 10 illustrates an example of a computing system environment onwhich aspects of the invention may be implemented.

DETAILED DESCRIPTION

Systems and methods for separating a part from a surface during additivefabrication are provided. As discussed above, in additive fabrication aplurality of layers of material may be formed on a build platform. Insome cases, one or more of the layers may be formed so as to be incontact with a surface other than another layer or the build platform.For example, stereolithographic techniques may form a layer of resin soas to be in contact with an additional surface such as a container inwhich liquid resin is located.

To illustrate one exemplary additive fabrication technique in which apart is formed in contact with a surface other than another layer or thebuild platform, an inverse stereolithographic printer is depicted inFIGS. 1 and 2. Exemplary stereolithographic printer 100 forms a part ina downward facing direction on a build platform such that layers of thepart are formed in contact with a surface of a container in addition toa previously cured layer or the build platform. In the example of FIGS.1 and 2, stereolithographic printer 100 comprises build platform 4,container 6, axis 8 and liquid resin 10. A downward facing buildplatform 4 opposes the floor of container 6, which is filled with aphotopolymer resin 10. FIG. 1 represents a configuration ofstereolithographic printer 100 prior to formation of any layers of apart on build platform 4.

As shown in FIG. 2, a part 12 may be formed layerwise, with the initiallayer attached to the build platform 4. The container's floor may betransparent to actinic radiation, which can be targeted at portions ofthe thin layer of liquid photocurable resin resting on the floor of thecontainer. Exposure to actinic radiation cures a thin layer of theliquid resin, which causes it to harden. The layer 14 is at leastpartially in contact with both a previously formed layer and the surfaceof the container 6 when it is formed. The top side of the cured resinlayer typically bonds to either the bottom surface of the build platform4 or with the previously cured resin layer in addition to thetransparent floor of the container. In order to form additional layersof the part subsequent to the formation of layer 14, any bonding thatoccurs between the transparent floor of the container and the layer mustbe broken. For example, one or more portions of the surface (or theentire surface) of layer 14 may adhere to the container such that theadhesion must be removed prior to formation of a subsequent layer.

Techniques for reducing the strength of this bond may include inhibitingthe curing process or providing a highly smooth surface on the inside ofthe container. In many use cases, however, at least some force must beapplied to remove the cured resin layer from the container floor. Forexample, a force may be applied by rotating the container tomechanically separate the container from the part 12. FIG. 3 depictsexemplary stereolithographic printer 100 separating a part from thecontainer by pivoting the container 6 about a fixed axis 8 on one sideof the container, thereby displacing an end of the container distal tothe fixed axis a distance 18 (which may be any suitable distance). Thisstep involves a rotation of the container 6 away from the part 12 toseparate layer 16 from the container, which may be followed by arotation of the container back towards the part. In addition, the buildplatform 4 may move away from the container to create a space for a newlayer of liquid resin to form between the part and the container.Subsequent to this motion, a new layer of liquid resin is available forexposure and addition to the part being formed. Each step of theaforementioned curing and separating processes may continue until thepart is fully created. By progressively separating the part and thecontainer base, such as in the steps described above, the peak forceand/or total force necessary to separate the part and container may beminimized.

However, multiple problems may arise due to the application of forceduring the above-described processes. For example, in some use cases aforce may be applied to and/or through the part itself. A force appliedto the part may, in some use cases, cause the part to separate from thebuild platform, rather than the container, which may disrupt thefabrication process. In some use cases, a force applied to the part maycause deformation or mechanical failure of the part itself.

The inventors have recognized and appreciated that the above-describedproblems with the separation processes may be reduced by minimizingforces applied to the part by applying such forces gradually and/orevenly to the part. While a higher force may provide fast separation ofthe part and the container, it may run a greater risk of deforming thepart. A lower force, in contrast, may produce a more precise printedpart with lower risk of deformation. By applying force gradually to apart, such as by performing a “peeling” process in which the forcegradually increases over time and/or is maintained at a lower force onthe part for a longer time, the part may be separated from the containerusing a minimal amount of force. Alternatively, or additionally,applying force evenly to a part may minimize the force applied to eachregion of the part. For example, force applied to a part may cause alarge force to be applied to a particular localized region of the part,e.g., due to the geometry of that region and a smaller force to beapplied to the remainder of the part. This may result in the localizedregion being deformed or otherwise negatively impacted by the largeforce. By instead applying force evenly to the part, deformation of oneor more regions of the part due to higher localized forces acting in theregions may be avoided.

“Separation” of a part from a surface, as used herein, refers to theremoval of adhesive forces connecting the part to the surface. It maytherefore be appreciated that, as used herein, a part and a surface maybe separated via the techniques described herein, though immediatelysubsequent to the separation may still be in contact with one another(e.g., at an edge and/or corner) so long as they are no longer adheredto one another.

The inventors have further recognized and appreciated that performing apeel by bending the container may provide a way to apply separationforces gradually and/or evenly to a part. Bending of the surface of thecontainer may naturally minimize forces applied to the part since acontainer that is curved relative to the region of contact between thepart and a surface may provide the gradual and/or even application offorce that aids the minimization of force.

In some embodiments, performing a peel includes bending a container.Bending the container may result in a more gradual and/or even peel, asdiscussed above, relative to a peel operation in which the container is,for example, kept rigid and rotated. The container may be bent in anysuitable way, including around any number of fixed points, such that thepart separates from the container while the fixed points remain in placeand such that the container does not rotate around the fixed points. Forexample, the container may be pulled down (e.g., away from the buildplatform) while one or more points of the container are fixed, such thata layer of a part in contact with the container is gradually peeled fromthe container. Bending the container may provide a more gradual peel ofa layer with forces more evenly applied to the part compared to a peeloperation that rotates the container (e.g., exemplary stereolithographicprinter 100 shown in FIG. 3, and discussed above). In some use cases,the container is bent such that its curvature increases. For example, insome use cases the container may be bent from a flat, or substantiallyflat, configuration into a convex or concave configuration.

In some embodiments, one or more fixed points of the container aroundwhich a container is bent are formed by mechanical fastening and/or byadhering those fixed points such that the container does not move and/orrotate about those points. For example, one or more points of acontainer may be attached to a frame (e.g., via one or more fasteners,via one or more adhesives and/or otherwise) so that a force applied toanother region of the container may cause at least part of the containerto bend while the fixed point or points remain in place.

In some embodiments, bending of a container is achieved through activemeans, such as by using one or more force generators to actively pushand/or pull regions of the container. The one or more force generatorsmay be coupled to any suitable mechanism or mechanisms such thatactivation of a force generator causes a force to be applied to one ormore points of the container. In some embodiments, active bending of thecontainer is performed via one or more actuators, such as motors (e.g.,stepper motors). The one or more actuators may be controlled by anynumber of suitable controllers, including one or more general purposeprocessors, Application Specific Integrated Circuits (ASICs),Field-Programmable Gate Arrays (FPGAs) and/or combinations thereof.Bending via active means may reduce forces transmitted to the partcompared with passive means, such as by causing the container to bendvia motion of the build platform (i.e., so that the adhesive forcesbetween the build platform, part and container cause the container tobend). By using active means to apply a force to a region of thecontainer that is not close, or adjacent, to a layer of a part incontact with the container, compressive forces that might otherwise beapplied to the part may be reduced.

In some embodiments, the build platform may move during a peel operationin addition to bending of the container. Moving the build platform may,in some use cases, aid separation of the part from the container. Forexample, the build platform may be moved toward the container while thecontainer is being bent, thereby further reducing forces applied to oneor more regions of the part. The build platform may be movedsimultaneously with the bending of the container and/or subsequent tobending being completed. Where the container is bent through activemeans, as described above, movement of the build platform may provide anadditional mechanism with which to control forces applied to a part incontact with the container. For example, separation of a part from acontainer performed solely by moving the build platform upwards can onlybe adjusted by altering the speed of the build platform. In contrast,separation performed using active means in addition to the movement ofthe build platform may adjust the relative speed and timing of the twomotions, thus providing greater control over the forces duringseparation.

In some embodiments, the container may be rotated during a peeloperation in addition to bending of the container. Rotating thecontainer may, in some use cases, aid separation of the part from thecontainer. For example, the container may be rotated away from the buildplatform while the container is being bent, thereby further reducingforces applied to one or more regions of the part. The container may berotated simultaneously with the bending of the container and/orsubsequent to bending being completed.

As discussed above, the container may be bent around one or more fixedpoints. In some embodiments, the one or more fixed points include an endof the container. For example, an end of the container may be keptsubstantially fixed while one or more forces are applied to one or moreportions of the container, thereby causing the container to bend. An endof the container may, for example, include a point at which a bottomsurface of the container meets a side surface of the container (of whichthere may be multiple such points). Motion of the portion or portions ofthe container may be in any direction, such as upwards (e.g., towardsthe build platform) and/or downwards (e.g., away from the buildplatform). In some embodiments, the container is bent around one or morefixed points in proximity to a part that is in contact with thecontainer. This may reduce forces applied to the part by simultaneouslypeeling two sides of the layer away from the container.

In some embodiments, the container comprises a material that is able tobe repeatedly elastically deformed without premature failure. Asdiscussed above, the container may hold a fabrication material, such asa liquid photopolymer, and provide a substantially flat surface on whichto form a layer of a part. Accordingly, the container should generallybe sufficiently rigid to perform these functions. However, in order tobend a sufficient amount to separate a part from the container, thecontainer may also have some flexibility. A non-limiting list ofexemplary materials from which the container may be formed include oneor more polymeric materials, such as Polyethylene Terephthalate (PET),Low-Density Polyethylene (LDPE), High-Density Polyethylene (HDPE),Poly(methyl methacrylate) (PMMA), Polydimethylsiloxane (PDMS), PolyvinylChloride (PVC), Polypropylene (PP), and/or any acrylic plastic. In someembodiments, the inventors have found that appropriate materials for thecontainer have a stiffness such that the container deflects a distancebetween 10-50 mm with an application of force between 5-25 N.Alternatively, or additionally, in some embodiments a suitable containermay be capable of substantial deflection with a peak strain of no morethan 5-10%, and preferably less than 5%.

Subsequent to the part being separated from the container, the containerand/or build platform may move in preparation for a subsequent layer ofthe part being formed. This movement may be a reverse motion of themotion used to separate the part from the container, though mayalternatively be a different motion. In embodiments in which thecontainer and part both move, any flexure and/or motion of the containersubsequent to the separation of the container and part may, or may not,be coordinated in the manner described above for bending the container.For example, it may be beneficial to move the container and/or part to anew position in preparation for forming a new layer of the part morerapidly than the motion used to separation the container from the part,e.g., to reduce the total time needed to form the part.

Additional improvements may be readily implemented to reduce peel speedand/or to limit the maximum and/or overall force applied. In someembodiments, a force generator may be modified to apply force in anon-linear fashion, for example through a guide channel which shapes thedirection of the force applied. Additionally, or alternatively, a forcegenerator may apply a force at an angle offset from the normal of thecontainer's surface. In some embodiments, the container may be formedwith a non-uniform bottom container thickness such that the bottomthickness increases further away from the force generator. Suchdifferential stiffness may advantageously require a higher force to beapplied in order to deflect the far side of the container (the sidefurthest from the force generator). This requirement of a higher forcemay effectively maintain adhesion of the far side of the part to thecontainer as the peel begins at the edge near the force generator. Insome embodiments, the acrylic resin container may be pre-tensioned suchthat an initial configuration of the container is deflected towards thebuild platform. Such a configuration may tend to counteract downwardforces caused by the weight of the resin and the downward force of thebuild platform so that the container and the platform are parallelduring the fabrication phase. In the absence of such a configuration,the downward force of the build platform during fabrication could causethe container to curve and create a non-uniform print thickness.

In some embodiments, part or the entire floor of the container is formedfrom a thin film. Using a flexible, thin film as at least part of thefloor of the container may decrease the overall force applied to a partbeing formed by allowing a peeling edge to propagate inward from most orall of the outer edge of the contact area between the part and the film,rather than from a discrete number of sides. The thin film may beconfigured to behave like a thin sheet, rather than a flexible beam asdescribed above. The thin film may be separated from the part via activeand/or passive means. For example, an active means may pull on the thinfilm to initiate and/or propagate a peeling edge. Alternatively, oradditionally, a passive means, such as a motion of the build platform,may be performed to initiate and/or propagate peeling of the film fromthe part.

Following below are more detailed descriptions of various conceptsrelated to, and embodiments of, systems and methods for separating apart from a surface during additive fabrication. It should beappreciated that various aspects described herein may be implemented inany of numerous ways. Examples of specific implementations are providedherein for illustrative purposes only. In addition, the various aspectsdescribed in the embodiments below may be used alone or in anycombination, and are not limited to the combinations explicitlydescribed herein.

Although the embodiments herein are primarily disclosed with respect tothe Form 1 3D Printer sold by Formlabs, Inc., the Assignee of thepresent application, and with respect to stereolithography, thetechniques described herein may be equally applicable to other systems.In some embodiments, structures fabricated via one or more additivefabrication techniques as described herein may be formed from, or maycomprise, a plurality of layers. For example, layer-based additivefabrication techniques may fabricate an object by formed a series oflayers, which may be detectable through observation of the object, andsuch layers may be any size, including any thickness between 10 micronsand 500 microns. In some use cases, a layer-based additive fabricationtechnique may fabricate an object that includes layers of differentthickness.

Although particular systems and methods for separating a part from asurface during additive fabrication have been described and shownherein, it is envisioned that the functionality of the various methods,systems, apparatus, objects, and computer readable media disclosedherein may be applied to any now known or hereafter devised additivefabrication technique wherein it is desired to separate a part from asurface during fabrication.

As discussed above, the inventors have recognized and appreciated thatmultiple problems may arise due to the application of force during thepeeling process described above and depicted in FIG. 3. In particular,as shown in FIG. 3, forces applied to the part during rotation of thecontainer may be undesirable, as they may lead to increased partdistortion and/or failure.

FIGS. 4A-B depict an exemplary additive fabrication device configured toseparate a part from a surface by bending the surface, according to someembodiments. Exemplary inverse stereolithographic printer 400 includes aflexible container 2 located opposite to build platform 4. The flexiblecontainer 2 contains uncured photopolymer resin 10. Attached to thebuild platform 4 is a part 12, which in the example of FIG. 4A comprisesa number of layers formed by additive fabrication including a firstlayer at which the part is attached to the build platform. A forcegenerator 28 is affixed to one edge of the container, while the otherend of the container 30 is fixed in place relative to the buildplatform. As the flexible container 2 bends downward, a separation edgeor mechanical peel 16 initiates. The flexible container 2 comprises oneor more flexible materials, examples of which are described above.

As shown in the example of FIG. 4A, one side of the flexible container 2is fixed while the opposing side of the flexible container is coupled toa force generator 28. A force generated by force generator 28 may begenerated in any suitable way, such as with a stepper motor. When theforce generator is activated, the flexible nature of the containercombined with the fixed end 30 allows the container to deflect or bend,as shown in FIG. 4A, instead of pivoting as shown in FIG. 3. In theexample of FIG. 4A, as the floor of the flexible container bendsdownward, the build platform 4 remains stationary. The bending ofcontainer 2 may, in some use cases, be considered analogous to thebending of a loaded cantilever beam.

In the example of FIG. 4A, adhesive forces between the part 12 and thefloor of the flexible container 2 may initially resist the deflection ofthe container floor. As such, the part 12 may tend to exert an upwardpull on the flexible container 2 through the adhered cured resin layer14. The force generator 28, however, continues to exert a downwardsforce on the flexible container 2 along one side, thus deflecting theflexible container 2. As the flexible container 2 is deflected, forceexerted on the part 12 through the adhered layer 14 tends to increase.As the force builds, it eventually becomes great enough to overcome theadhesion force on the edge of the part 12 proximal to the forcegenerator. The layer of the part in contact with the container 14 maythen begin to separate or “peel” from the container at a “leading” edge16. A void created at the leading edge may begin to fill with resin andthe peel propagates across the part 12 until the part 12 is fullyseparated from the flexible container 2. Once the part is separated fromthe container as shown in FIG. 4B, the build platform 4 may move upwardwith the part. The flexible container 2 then returns to a positionparallel to the build platform 4 and the part 12. The upward motionrefreshes and replaces the layer of uncured resin 10 and the next layerof the build can progress. Each step of the aforementioned curing andpeeling processes may then continue until the part is fully created.

As discussed above, some embodiments may advantageously provide for amore gradual separation of a part from a surface than techniquesdescribed above, and/or may advantageously lower the force needed toperform said separation. With a slower application of a peel force, apart may separate with lower peak forces and less distortion overallbecause the peel is able to progress more gradually across the part.

Some embodiments may achieve one or more of the above advantages bymaintaining adhesion between a part and the surface. For example, asshown in FIGS. 4A-B, a peel may initially propagate from an edge of thepart proximal to a force generator 28. Because container 2 is flexible,it is partially kept in place by the upward pull of the forces providedby the adhered layer 14. In contrast, in the exemplary system of FIG. 3,the separation would tend to occur globally across the layer since themagnitude of the attachment force in relation to a force needed toelastically deform the beam is trivial. Therefore, once the peel isinitiated, a non-flexible container such as that shown in the example ofFIG. 3 would continue to separate downward globally in the fixed pivotmotion as shown. In the flexible container system depicted in FIGS.4A-B, however, because one end of the container is fixed, the beam willbend and the curvature will be greatest towards the fixed edge 30.Stated otherwise, near the fixed edge the beam will remain flat for thelongest period and thereby facilitate the adherence of cured resin 14 onthe far side of the part 12 to the container floor while the separationprogresses.

While the overall and maximum separation forces may be reduced in theexample of FIGS. 4A-B, in some use cases the forces may still benon-uniform across the part 12. This non-uniformity in the applied forcemay be undesirable as it may lead to increased part distortion and/orfailure. Since the curvature of the floor of the container is greatestnear the fixed edge 30, the peel may progress slowest at that edge.Accordingly, areas of the part 12 closer to the force generator 28 mayhave increased part distortion and failure.

FIGS. 5A-B depict an alternate embodiment that addresses some of theproceeding issues, according to some embodiments. In the example ofFIGS. 5A-B, a flexing force is applied to two or more sides of theflexible container 2 by two or more force generators 28 while keeping atleast fixed point 31 held in place. In exemplary inversestereolithographic printer 500, therefore, instead of having a fixedside of the container, the container has opposing forces on two or moresides along with one or more fixed points between the two sides thatwork in concert to bend the container in a concave manner across thecontainer.

In some use cases, by applying a flexing force from two directions partpeeling may be initiated at multiple locations. For example, the leftand right sides of layer 14 may begin peeling independently of oneanother (at the same time, or at different times), and the final regionof the layer to separate from the container may be located between theleft and right sides of the layer. Once the part 12 and the mostrecently cured resin layer 14 are separated from the flexible resincontainer 2, the flexed sides of the resin container may return to theiroriginal position with the resin container parallel to the part 12 andthe build platform 4. As the sides return to the original position, theupward motion replaces the layer of uncured resin 10 and the next layerof the build can progress. Each step of the aforementioned curing andpeeling processes may continue until the part is fully created. Multiplepeel sites may, in some use cases, work to reduce overall force needed,decrease distortion across the part by more evenly applying forces,and/or reduce peel time.

It will be appreciated that substantially the same result as shown inFIGS. 5A-B may equally be effected by keeping one or more points at theends of the container fixed and applying a force between the ends in anupward direction while moving the build platform upward. As such,exemplary peeling processes that include bending of a containerdescribed here, including but not limited to those discussed in relationto FIGS. 4A-B and FIGS. 5A-B, may perform said bending in any suitableway such that the container bends relative to a part and/or buildplatform. It will be appreciated that, in general, such motion may beeffected by any suitable combination of applying force to the container,keeping one or more points of the container fixed, rotating thecontainer about an axis and/or moving the build platform, and that theparticular examples discussed herein are simply illustrative of thesetechniques.

FIGS. 6A-C illustrate an exemplary additive fabrication deviceconfigured to separate a part from a surface using a flexible film,according to some embodiments. Exemplary additive fabrication device 600includes a container formed from a thin film 22 and sides 20, whichholds resin 10. Thin film 22 may comprise any highly flexible and/ornon-reactive material, such as Teflon® (or any otherpolytetrafluoroethylene-based formula). The sides of the resin container20 may be comprised of a more rigid material such as an acrylic. Thefilm may have any suitable thickness such that the film is thick enoughto maintain structural integrity through the fabrication process and isthin enough to be easily removed from the part as described herein. Insome embodiments, the thin film has a thickness between 0.002″ and0.02″. In some embodiments, the thin film has a thickness equal to orgreater than 0.05″ and less than or equal to 0.01″. Thin film 22 may befixed to the resin container sides 20 or may be adjustably tensionedbetween them. Exemplary additive fabrication device 600 includes a wiper24, to be discussed below.

As shown in FIG. 6A, a layer of cured resin 14 of a part 12 may adhereto the flexible floor of the container 22 during the fabricationprocess. As shown in FIG. 6B, the build platform and part may be liftedupward with adhesion forces causing the film 22 to deform. The flexiblefilm 22 is able to deflect upward with the part until the necessaryseparation force is generated by the upward movement of the part and thedownward pull of the container floor. A mechanical peel 16 then beginsat the outer edges of the part and propagates inward until the part isseparated, as shown in FIG. 6C.

Using a flexible film layer as part or the entire floor of the containermay decrease the overall force applied to the part by allowing thepeeling edge to propagate inward from the entire outer edge rather thana discrete number of sides. In the example of FIGS. 6A-C, theflexibility of the resin container may be such that the floor of theresin container 22 behaves like a thin sheet, rather than like aflexible beam. This difference may be typified by the extent to whichthe floor of the resin container propagates beam loading forces acrossthe floor of the container. Flexible resin containers described above(e.g., as relating to FIGS. 4A-B and 5A-B) may tend to propagate loadacross the entire floor of the container, thus deflecting globallyacross the layer in contact with the container. Using a film may resultin the load being concentrated and minimally propagating deflection.With a highly elastic film layer, the adhesion force may be sufficientto deform the film layer and ensure the peel progresses gradually acrossthe part. Further, a film layer 22 may reduce peel discrepancies basedon part placement. Because each part peels independently with alocalized peel, the placement of the part 12 relative to the containersides 20 may become less relevant.

In some use cases, the use of a highly flexible film may result in theweight of resin and force of the build platform and part to causeunwanted “sagging” deformation in the film. Such sagging may partiallyaddressed by the use of a wiper. FIGS. 7A-C depict the use of such awiper 24 in exemplary container 700 having thin film 22, ends 20 andcomprising resin 10. In the example of FIGS. 7A-C, the wiper lifts thefilm up towards the bottom of the part or build platform and sopositions the film prior to each build layer to ensure a uniformthickness of resin between the build platform 4 and the resin tank floor22.

As shown in the exemplary progression from FIG. 7A to FIG. 7B to FIG.7C, the wiper may move from one side of the container to the other whilepushing the sag out of the film until it is sufficiently parallel to thebuild platform 4 (see FIGS. 6A-C). The film floor may be held in placeby suction forces between the container floor 22 and the build platform4 or part 12. This suction may depend on the viscosity of the resinand/or on the size of a part currently being fabricated. While the wiper24 is depicted as a cylindrical roller in FIG. 7, the wiper may be ofany suitable shape and may progress across the film floor in anysuitable way, such as from one side to the other as shown in FIGS. 7A-C,or in a coordinated pivoting motion like windshield wipers. Followingthis motion, a thickness of resin suitable for fabricating a layer of apart may be left between the film and either the build platform 4, orafter fabrication has commenced, the part 12. In some embodiments, thewiper may proceed below the film such that it accelerates smoothly withminimal frictional forces. Moving the wiper too slowly could allow thefilm floor 22 to sag again behind the wiper, but moving the wiper tooquickly may cause undesirable friction as the blade accelerates. In someembodiments, the wiper speed is between 65 mm/s and 75 mm/s.

In some embodiments, the viscosity of the resin and suction forcescreated between the build platform 4 and the floor of the container 22are utilized to maintain the correct position of the film while the nextlayer is printed. However, in some use cases, such forces may beinsufficient to hold the film in place. In such use cases, it may beadvantageous to apply a further upward force 26 across the floor of theresin container as depicted in FIG. 8 to ensure the floor of the resincontainer 22 is parallel to the build platform when filled with resinand the weight of the part and build platform. In one embodiment, suchforce may be provided by introducing a pressure difference between thelower and upper (resin contacting) sides of the thin film. The pressureadded may be sufficient to overcome the weight of the resin 10 and thefilm floor 22. Such a pressure difference may be provided through anysuitable source, including standard atmospheric pumps, fans and/orcompressed gas. In some embodiments, a pressure difference may becreated by use of a fan placed at the outside of an enclosure locatedbelow the film. In some embodiments, the enclosure may be sealed toallow higher pressures to build. In some embodiments, pressure may becreated using a standard computer fan, such as a Rosewill RFX-100 90 mmcase fan.

FIG. 9 illustrates a flow chart of a process suitable for separating apart from a surface during additive fabrication, according to someembodiments. Method 900 may be performed by any suitable additivefabrication apparatus, including but not limited to a stereolithographicprinter as described above, for example in the exemplary embodimentshown in FIGS. 4A-B and/or FIGS. 5A-B.

In act 901, a first layer of material is formed via additivefabrication. The first layer of material may be formed at any timeduring additive fabrication of a part. For example, the first layer maybe the sole layer formed (e.g., on a build platform), or may be the mostrecently formed layer and may be in contact with one or more previouslyformed layers.

In act 902, the container is bent around one or more fixed points. Asdiscussed above, motion of any region of the container may be active orpassive. In embodiments in which the container is bent via active means,the bending may be effected via one or more force generators, such asactuators. In act 902, bending the container causes at least the firstlayer of material to separate from the container via the peel operationdescribed above, in act 903.

FIG. 10 illustrates an example of a suitable computing systemenvironment 1000 on which aspects of the invention may be implemented.For example, the computing system environment 1000 may be used toinstruct one or more force generators (e.g., actuators) to apply a forceto one or more regions of a container, to move a build platform, to movea wiper, or any combinations thereof. Such a computing environment mayrepresent a home computer, a tablet, a mobile device, a server and/orany another computing device.

The computing system environment 1000 is only one example of a suitablecomputing environment and is not intended to suggest any limitation asto the scope of use or functionality of the invention. Neither shouldthe computing environment 1000 be interpreted as having any dependencyor requirement relating to any one or combination of componentsillustrated in the exemplary operating environment 1000.

Aspects of the invention are operational with numerous other generalpurpose or special purpose computing system environments orconfigurations. Examples of well-known computing systems, environments,and/or configurations that may be suitable for use with the inventioninclude, but are not limited to, personal computers, server computers,hand-held or laptop devices, multiprocessor systems,microprocessor-based systems, set top boxes, programmable consumerelectronics, network PCs, minicomputers, mainframe computers,distributed computing environments that include any of the above systemsor devices, and the like.

The computing environment may execute computer-executable instructions,such as program modules. Generally, program modules include routines,programs, objects, components, data structures, etc. that performparticular tasks or implement particular abstract data types. Theinvention may also be practiced in distributed computing environmentswhere tasks are performed by remote processing devices that are linkedthrough a communications network. In a distributed computingenvironment, program modules may be located in both local and remotecomputer storage media including memory storage devices.

With reference to FIG. 10, an exemplary system for implementing aspectsof the invention includes a general purpose computing device in the formof a computer 1010. Components of computer 1010 may include, but are notlimited to, a processing unit 1020, a system memory 1030, and a systembus 1021 that couples various system components including the systemmemory to the processing unit 1020. The system bus 1021 may be any ofseveral types of bus structures including a memory bus or memorycontroller, a peripheral bus, and a local bus using any of a variety ofbus architectures. By way of example, and not limitation, sucharchitectures include Industry Standard Architecture (ISA) bus, MicroChannel Architecture (MCA) bus, Enhanced ISA (EISA) bus, VideoElectronics Standards Association (VESA) local bus, and PeripheralComponent Interconnect (PCI) bus also known as Mezzanine bus.

Computer 1010 typically includes a variety of computer readable media.Computer readable media can be any available media that can be accessedby computer 1010 and includes both volatile and nonvolatile media,removable and non-removable media. By way of example, and notlimitation, computer readable media may comprise computer storage mediaand communication media. Computer storage media includes both volatileand nonvolatile, removable and non-removable media implemented in anymethod or technology for storage of information such as computerreadable instructions, data structures, program modules or other data.Computer storage media includes, but is not limited to, RAM, ROM,EEPROM, flash memory or other memory technology, CD-ROM, digitalversatile disks (DVD) or other optical disk storage, magnetic cassettes,magnetic tape, magnetic disk storage or other magnetic storage devices,or any other medium which can be used to store the desired informationand which can accessed by computer 1010. Communication media typicallyembodies computer readable instructions, data structures, programmodules or other data in a modulated data signal such as a carrier waveor other transport mechanism and includes any information deliverymedia. The term “modulated data signal” means a signal that has one ormore of its characteristics set or changed in such a manner as to encodeinformation in the signal. By way of example, and not limitation,communication media includes wired media such as a wired network ordirect-wired connection, and wireless media such as acoustic, RF,infrared and other wireless media. Combinations of the any of the aboveshould also be included within the scope of computer readable media.

The system memory 1030 includes computer storage media in the form ofvolatile and/or nonvolatile memory such as read only memory (ROM) 1031and random access memory (RAM) 1032. A basic input/output system 1033(BIOS), containing the basic routines that help to transfer informationbetween elements within computer 1010, such as during start-up, istypically stored in ROM 1031. RAM 1032 typically contains data and/orprogram modules that are immediately accessible to and/or presentlybeing operated on by processing unit 1020. By way of example, and notlimitation, FIG. 10 illustrates operating system 1034, applicationprograms 1035, other program modules 1036, and program data 1037.

The computer 1010 may also include other removable/non-removable,volatile/nonvolatile computer storage media. By way of example only,FIG. 10 illustrates a hard disk drive 1041 that reads from or writes tonon-removable, nonvolatile magnetic media, a magnetic disk drive 1051that reads from or writes to a removable, nonvolatile magnetic disk1052, and an optical disk drive 1055 that reads from or writes to aremovable, nonvolatile optical disk 1056 such as a CD ROM or otheroptical media. Other removable/non-removable, volatile/nonvolatilecomputer storage media that can be used in the exemplary operatingenvironment include, but are not limited to, magnetic tape cassettes,flash memory cards, digital versatile disks, digital video tape, solidstate RAM, solid state ROM, and the like. The hard disk drive 1041 istypically connected to the system bus 1021 through an non-removablememory interface such as interface 1040, and magnetic disk drive 1051and optical disk drive 1055 are typically connected to the system bus1021 by a removable memory interface, such as interface 1050.

The drives and their associated computer storage media discussed aboveand illustrated in FIG. 10, provide storage of computer readableinstructions, data structures, program modules and other data for thecomputer 1010. In FIG. 10, for example, hard disk drive 1041 isillustrated as storing operating system 1044, application programs 1045,other program modules 1046, and program data 1047. Note that thesecomponents can either be the same as or different from operating system1034, application programs 1035, other program modules 1036, and programdata 1037. Operating system 1044, application programs 1045, otherprogram modules 1046, and program data 1047 are given different numbershere to illustrate that, at a minimum, they are different copies. A usermay enter commands and information into the computer 1010 through inputdevices such as a keyboard 1062 and pointing device 1061, commonlyreferred to as a mouse, trackball or touch pad. Other input devices (notshown) may include a microphone, joystick, game pad, satellite dish,scanner, or the like. These and other input devices are often connectedto the processing unit 1020 through a user input interface 1060 that iscoupled to the system bus, but may be connected by other interface andbus structures, such as a parallel port, game port or a universal serialbus (USB). A monitor 1091 or other type of display device is alsoconnected to the system bus 1021 via an interface, such as a videointerface 1090. In addition to the monitor, computers may also includeother peripheral output devices such as speakers 1097 and printer 1096,which may be connected through a output peripheral interface 1095.

The computer 1010 may operate in a networked environment using logicalconnections to one or more remote computers, such as a remote computer1080. The remote computer 1080 may be a personal computer, a server, arouter, a network PC, a peer device or other common network node, andtypically includes many or all of the elements described above relativeto the computer 1010, although only a memory storage device 1081 hasbeen illustrated in FIG. 10. The logical connections depicted in FIG. 10include a local area network (LAN) 1071 and a wide area network (WAN)1073, but may also include other networks. Such networking environmentsare commonplace in offices, enterprise-wide computer networks, intranetsand the Internet.

When used in a LAN networking environment, the computer 1010 isconnected to the LAN 1071 through a network interface or adapter 1070.When used in a WAN networking environment, the computer 1010 typicallyincludes a modem 1072 or other means for establishing communicationsover the WAN 1073, such as the Internet. The modem 1072, which may beinternal or external, may be connected to the system bus 1021 via theuser input interface 1060, or other appropriate mechanism. In anetworked environment, program modules depicted relative to the computer1010, or portions thereof, may be stored in the remote memory storagedevice. By way of example, and not limitation, FIG. 10 illustratesremote application programs 1085 as residing on memory device 1081. Itwill be appreciated that the network connections shown are exemplary andother means of establishing a communications link between the computersmay be used.

The various methods or processes outlined herein may be implemented inany suitable hardware. Additionally, the various methods or processesoutlined herein may be implemented in a combination of hardware and ofsoftware executable on one or more processors that employ any one of avariety of operating systems or platforms. For example, the variousmethods or processes may utilize software to instruct a processor toactivate one or more actuators to perform motions such as thosedescribed herein, such as motion of one or more regions of a containerand/or of a build platform. Example of such approaches are describedabove. However, any suitable combination of hardware and software may beemployed to realize any of the embodiments discussed herein.

In this respect, various inventive concepts may be embodied as at leastone non-transitory computer readable storage medium (e.g., a computermemory, one or more floppy discs, compact discs, optical discs, magnetictapes, flash memories, circuit configurations in Field Programmable GateArrays or other semiconductor devices, etc.) encoded with one or moreprograms that, when executed on one or more computers or otherprocessors, implement the various embodiments of the present invention.The non-transitory computer-readable medium or media may betransportable, such that the program or programs stored thereon may beloaded onto any computer resource to implement various aspects of thepresent invention as discussed above.

The terms “program” or “software” are used herein in a generic sense torefer to any type of computer code or set of computer-executableinstructions that can be employed to program a computer or otherprocessor to implement various aspects of embodiments as discussedabove. Additionally, it should be appreciated that according to oneaspect, one or more computer programs that when executed perform methodsof the present invention need not reside on a single computer orprocessor, but may be distributed in a modular fashion among differentcomputers or processors to implement various aspects of the presentinvention.

Computer-executable instructions may be in many forms, such as programmodules, executed by one or more computers or other devices. Generally,program modules include routines, programs, objects, components, datastructures, etc. that perform particular tasks or implement particularabstract data types. Typically, the functionality of the program modulesmay be combined or distributed as desired in various embodiments.

Various inventive concepts may be embodied as one or more methods, ofwhich examples have been provided. For example, methods of separating apart from a surface during additive fabrication have been providedherein. The acts performed as part of any method described herein may beordered in any suitable way. Accordingly, embodiments may be constructedin which acts are performed in an order different than illustrated,which may include performing some acts simultaneously, even though theseacts may have been shown as sequential acts in illustrative embodiments.

All definitions, as defined and used herein, should be understood tocontrol over dictionary definitions, definitions in documentsincorporated by reference, and/or ordinary meanings of the definedterms.

The indefinite articles “a” and “an,” as used herein, unless clearlyindicated to the contrary, should be understood to mean “at least one.”

As used herein, the phrase “at least one,” in reference to a list of oneor more elements, should be understood to mean at least one elementselected from any one or more of the elements in the list of elements,but not necessarily including at least one of each and every elementspecifically listed within the list of elements and not excluding anycombinations of elements in the list of elements. This definition alsoallows that elements may optionally be present other than the elementsspecifically identified within the list of elements to which the phrase“at least one” refers, whether related or unrelated to those elementsspecifically identified.

The phrase “and/or,” as used herein, should be understood to mean“either or both” of the elements so conjoined, i.e., elements that areconjunctively present in some cases and disjunctively present in othercases. Multiple elements listed with “and/or” should be construed in thesame fashion, i.e., “one or more” of the elements so conjoined. Otherelements may optionally be present other than the elements specificallyidentified by the “and/or” clause, whether related or unrelated to thoseelements specifically identified. Thus, as a non-limiting example, areference to “A and/or B”, when used in conjunction with open-endedlanguage such as “comprising” can refer, in one embodiment, to A only(optionally including elements other than B); in another embodiment, toB only (optionally including elements other than A); in yet anotherembodiment, to both A and B (optionally including other elements); etc.

As used herein, “or” should be understood to have the same meaning as“and/or” as defined above. For example, when separating items in a list,“or” or “and/or” shall be interpreted as being inclusive, i.e., theinclusion of at least one, but also including more than one, of a numberor list of elements, and, optionally, additional unlisted items. Onlyterms clearly indicated to the contrary, such as “only one of” or“exactly one of,” will refer to the inclusion of exactly one element ofa number or list of elements. In general, the term “or” as used hereinshall only be interpreted as indicating exclusive alternatives (i.e.“one or the other but not both”) when preceded by terms of exclusivity,such as “either,” “one of,” “only one of,” or “exactly one of.”

The phraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting. The use of“including,” “comprising,” “having,” “containing”, “involving”, andvariations thereof, is meant to encompass the items listed thereafterand additional items.

Having described several embodiments of the invention in detail, variousmodifications and improvements will readily occur to those skilled inthe art.

For example, techniques of separating a portion of a part formed throughadditive fabrication from a surface were described. These techniques maybe applied in other contexts. For example, any additive fabricationprocess in which a portion of a part being formed becomes in any wayattached to a surface other than another portion of the part or a buildplatform may utilize techniques as described herein. Such modificationsand improvements are intended to be within the spirit and scope of theinvention. Accordingly, the foregoing description is by way of exampleonly, and is not intended as limiting.

What is claimed is:
 1. An additive fabrication apparatus configured toform a plurality of layers of material on a build platform, comprising:a container; the build platform; one or more force generators coupled tothe container; and at least one controller configured to: subsequent toformation of a layer of material in contact with the container, operatethe one or more force generators to apply a force to a portion of thecontainer, thereby actively bending the container away from the buildplatform, whilst simultaneously moving the build platform relative tothe container, such that the layer of material separates from thecontainer.
 2. The apparatus of claim 1, wherein bending the containercomprises moving at least a portion of the container via the one or moreforce generators while anchoring the container at least one fixed point.3. The apparatus of claim 2, wherein the at least one fixed pointincludes a first end of the container.
 4. The apparatus of claim 3,wherein bending the container comprises moving a second end of thecontainer away from the build platform.
 5. The apparatus of claim 1,wherein the container comprises one or more polymers.
 6. The apparatusof claim 5, wherein the one or more polymers include one or more of:Polyethylene Terephthalate (PET), Low-Density Polyethylene (LDPE),High-Density Polyethylene (HDPE), Poly(methyl methacrylate) (PMMA),Polydimethylsiloxane (PDMS), Polyvinyl Chloride (PVC), and/orPolypropylene (PP).
 7. The apparatus of claim 1, wherein the at leastone controller is further configured to move the build platform awayfrom the container concurrently with the active bending of thecontainer.
 8. The apparatus of claim 1, wherein the at least onecontroller is further configured to rotate the container around a firstfixed point.